The Ne-22(p,gamma)Na-23 reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E-p = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E-p = 71 and 105 keV. Here, new Ne-22(p,gamma)Na-23 data with high statistics and low background are reported. Stringent upper limits of 6 x 10(-11) and 7 x 10(-11) eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the Ne-22(p,gamma)Na-23 rate is now reduced by 3 orders of magnitude.

Direct Capture Cross Section and the Ep=71 and 105 keV Resonances in the Ne 22 (p,γ) Na 23 Reaction

Gervino, G.;
2018-01-01

Abstract

The Ne-22(p,gamma)Na-23 reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at E-p = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at E-p = 71 and 105 keV. Here, new Ne-22(p,gamma)Na-23 data with high statistics and low background are reported. Stringent upper limits of 6 x 10(-11) and 7 x 10(-11) eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the Ne-22(p,gamma)Na-23 rate is now reduced by 3 orders of magnitude.
2018
121
17
172701
172701
http://harvest.aps.org/bagit/articles/10.1103/PhysRevLett.121.172701/apsxml
https://arxiv.org/abs/1810.01628
Physics and Astronomy (all)
Ferraro, F.; Takács, M.P.; Piatti, D.; Cavanna, F.; Depalo, R.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C.G.; Caciolli...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1694160
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